PL178383B1 - Method of thermostatising the sets of injection moulding machines and sets of moulds used in processing plastic materials - Google Patents

Abstract

1. A method for regulating the temperature of injection molding units and mold units for processing plastics, with at least one temperature control circuit, during which the temperature is measured in a specific place and, as a result of comparing the set value with the actual value, the flow of the temperature-regulating medium changes, characterized by that temperature regulation is carried out in a process including the following stages: - calculation of heat dissipation during the cycle by dividing the time between time points Z1 and Z2 into equal parts, with time points Z 1 and Z2 being set in advance by impulses controlling the machine's operation, - preliminary determination of the desired heat dissipation, before starting the temperature regulation, - continuous measurement of the temperature of the exhausted medium and the feeding medium, - determination of the value of the WRG heat contained in the device when the device reaches thermal equilibrium, - storing the value of the contained heat in the next cycle as the desired value, based on the differences between the temperature of the exhausted medium and the temperature of the supply medium during the reference cycle, - comparison of the desired value with the instantaneous actual value measured during all subsequent cycles, - designation of the correction value for the temperature control pulse triggered in a given cycle based on deviation of the heat content from the reference cycle, in which the designated temperature control pulse starts at time point Z1, with the initial thermostatting process triggered at time point Z1, and the pulse ending the temperature regulation process triggered at the latest time point Z2. PL

Description

The subject of the invention is a method of temperature control of injection molding units and mold units for processing plastics. The invention particularly relates to injection molding units for processing crosslinkable polymers and to plastic processing molds having at least one temperature control circuit.

In injection molding, the thermal operating state of the mold, which is measured by the mold temperature, is one of the most important thermal quantities in addition to the cylinder temperature and the melt temperature. It has a significant influence on the flowability of the molten plastic, the cycle time and the quality of the moldings, in particular the surface quality, shrinkage and warping.

The thermal operating state of the plasticizing cylinder is critical to the processing of high molecular weight crosslinking polymers. Such materials require, when processed into compacts by injection molding, a relatively low temperature level while in the plasticizing cylinder in order to avoid premature cross-linking or partial cross-linking of the molding material. The amount of heat generated during the plasticization due to friction of the molding compound, i.e. by the processing of mechanical energy, is usually greater in the stationary, i.e. running-in, state of the machine than the amount of heat required to obtain the optimal viscosity of the molding compound.

The temperature of the molding compound or molten material in the screw / cylinder system must be controlled so that premature cross-linking reactions do not occur due to excessively high molding material temperatures. Accurate determination of the temperature of the molding material by adjusting the cylinder temperature has a significant impact on the quality of the moldings produced.

In practice, it has hitherto been possible to work only with thermostats, but they have some disadvantages, which will be detailed later in the description of the use of temperature control devices.

Various methods are known for controlling the thermal operating condition, i.e. the temperature control of injection molding machines.

In practice, it was only possible to work with temperature control devices until now. So far, work is still being done on introducing mold temperature regulation as an integral part of injection molding machines. The first variation consists in inserting the temperature control device into an injection molding machine (Plasta und Kautschuk 1982, issue 2, p. 86).

The temperature control device is therefore located in the immediate vicinity of the mold to avoid heat loss through the duct system. This solution leads to a low space requirement for setting up the injection molding machine, but the main disadvantages of this method of temperature control remain.

Various methods of thermal control of the operating state of injection molds are known.

In previous practice, only the work with temperature control devices could gain significance. So far, there is no work yet on introducing mold temperature control as an integral part of injection molding machines. The first variant is that the temperature control device is placed in the injection molding machine (Plasta und Kautschuk 1982, issue 2, p. 86).

The temperature control device is therefore located in the immediate vicinity of the mold to avoid heat loss caused by the duct system. Such a solution leads to

Low space requirement for setting up the injection molding machine, however, the basic disadvantages of this method of temperature control remain. First of all, it is an energetically unfavorable way of working and high costs of temperature control devices. DD-PS 203 011 discloses a method in which the cooling phase after injection is interrupted, followed by the temperature control phase, and then the cooling phase is restarted, which should continue until the residual energy content of the part is sufficient to heat the injection mold to a favorable temperature. for the next injection molding cycle.

The disadvantage of this method is primarily that the technological differences in heat dissipation of the individual cooling phases must be manually adapted to the duration of the cooling phase at the beginning of the production process by various throttling of the cooling water flow by means of control valves or by changing the settings of adjustable timers. This requires a considerable amount of work and places increased demands on the operating personnel. Moreover, when using this method, as with conventional temperature control devices, it is impossible to regulate unavoidable disturbances in the production flow, for example fluctuations in the temperature of the cooling water and the flow rate of the cooling water, changes in temperature, in particular the temperature of the melt, and the cycle time in their energetic effect. the quality of the part. Depending on the magnitude of the energetic impact of these disturbances, the thermodynamic state of the mold may change to a greater or lesser extent, and quality differences may occur in the manufactured moldings, resulting in loss. US-PS No. 4,420,446 describes a method of controlling the mold temperature in injection molding. The selected control temperature is hereby set as the set temperature. The mold temperature is measured in the immediate vicinity of the mold cavity. Depending on whether the temperature is higher or lower than the set temperature, the valves of the cooling circuit open or close. Moreover, when the preset upper and lower limit temperatures are exceeded upwards or downwards, optical and acoustic signaling is activated.

A similar solution whereby the heat supplied with the molten material should be used to control the temperature of the mold wall is described in the journal Plastverarbeiter 1984, issue 5, pp. 77-80. The temperature control is hereby controlled by a microprocessor by means of a thermal sensor. The temperature rise caused by the introduction of the molten material is measured in the mold contour, and a microprocessor controls the opening time of the solenoid valve system for the cooling water supply. There is a so-called impulse cooling, and the mold takes over the function of the heat exchanger.

ZEP0218919B1 is a known method of calibrating and correcting a mold temperature control device in injection molding machines, where the computer controls the closing and opening of the valves as a function of the temperature difference in the molds after a measuring period with fully open valves and a measuring period with closed valves. After reaching the set temperature, two calibration cycles are carried out in which the elongation of the mold is tested by measuring decreasing or increasing the temperature. Based on the specified temperature differences, the computer calculates the valve opening times needed to maintain the specified set temperature. The temperature is regulated only on the basis of the instantaneous mold temperature measured. These known methods based on the same principle have the following disadvantages.

The close proximity of the temperature sensors to the mold contour, i.e. to the warmest zone of the mold, inevitably leads to the set temperature being exceeded during each injection operation, also during the approach, and thus to the release of cooling. Temperature control only as a function of the measured instantaneous temperature with the always existing inertia of thermal equalization between the molten material and the mold and between the coolant and the mold can lead to a temporary shift in the mold temperature control, and thus to mold temperatures that are clearly below or above the selected control temperature . Both the disturbances in the injection molding process, for example a reduced supply of coolant, and the unfavorable position of the cooling surface in relation to the mold contour in complicated molds, are not always sufficiently compensated by this method, so it is not always possible to adjust the temperature control conditions to the instantaneous ones. process parameters.

A further known method of temperature control (WO 92/08598) is to control the flow of the temperature control medium after calculating the average mold temperature or the average temperature of the exhaust medium, or after determining the average mold temperature or average exhaust temperature trend for several cycles performed. The average mold temperature is compared with the specified set temperature, and the cooling regime changes in the next cycle, if the average mold temperature differs from the specified set temperature. The place of temperature measurement in the mold or in the flow of the exhausted medium is not considered critical, which, however, is contrary to the information from practice.

About the opening time of the solenoid valves in the cycle in the above-described method are only general statements. First, the solenoid valve opens when the average temperature of the previous cycle is above the upper limit temperature, and second, when the average temperatures of a number of previous cycles indicate an upward trend around the set temperature. The opening time itself should depend on the degree of temperature change or on the value of the difference in relation to the accepted temperature range. At the same time, however, one does not go into the specific calculation formula implemented. The control of the mold temperature in the following cycle, carried out according to this method, disregards the sharp disturbances in the cycle. These disturbances are only then regulated by the relatively inertial mean temperature mechanism. It should be assumed that the described control generally lags behind the actual mold temperature and in particular, with the disruptions involved, without achieving the intended high process stability. Regarding the place of measurement and knowing that the temperature distribution in the mold creates a certain temperature field, practical experience in any determination of the place of measurement in the mold shows a reasonable doubt as to the achievement of the intended goals. When measuring the temperature of an exhausted medium, there are several critical points which more or less question the intended operation of the process. To calculate the average temperature of the depleted medium versus a given mold temperature, it is necessary to measure the temperature of the medium flowing through the entire cycle. This, in turn, causes continuous, if even choked, additional heat dissipation from the mold. In those applications where medium or even high mold temperatures are needed, the desired temperature level cannot be maintained in the mold. There is no measurement of the inflow temperature, which means that a significant factor influencing the thermal state of the mold operation remains without taking into account, and in the event of changes, it inevitably leads to deviations from the thermal state of the given mold. Moreover, the deviations of the mean return temperature from the specified target temperature in the event of a disturbance with a run-in machine, especially at high volumetric flows, are according to experience so small that it is not always possible to deliberately influence the flow duration of the temperature-regulating medium.

The essence of the method of temperature control of injection molding units and mold sets for processing plastics, with at least one temperature control circuit, during which the temperature is measured at a specific location and as a result of comparing the set value with the actual value, the flow of the temperature-regulating medium changes, according to the invention, temperature control is accomplished by a process including the following steps:

- calculation of heat dissipation during the cycle by dividing the time between time points Zji Znn r equal parts, liquidity points Zj i2 ₂ quauatalised earlier by the control pulses of the machine,

- preliminary determination of the desired heat dissipation, before starting temperature control,

- continuous temperature measurement of the exhausted medium and the feeding medium,

- determination of the heat value WRG contained in the device, when the device reaches thermal equilibrium,

178 383

- saving the value of the contained heat in the next cycle as the desired value, based on the difference between the temperature of the medium exhausted and the temperature of the supply medium during the reference cycle,

- comparing the desired value with the instantaneous actual value measured during all subsequent cycles,

- determination of the correction value for the temperature control pulse triggered in a given cycle based on the heat content deviation from the reference cycle, in which the determined temperature control pulse begins at time point Z ,, with the initial thermostating process triggered at time point Z ,, a pulse ending the temperature control process, triggered at the time point Z ₂ at the latest.

Preferably, the mold temperature is measured continuously at a location where the melt and the temperature regulating medium act equally.

Preferably, the temperature of the cylinder is measured continuously at a location where the heated molding compound and the temperature-regulating medium act equally.

Preferably, when controlling the mold temperature of an injection molding machine, as time Z! the start of the holding-in time is set, and the end of the mold opening movement is set as time point Z2.

Preferably, as time Z, the start of the injection operation is determined.

Preferably, when controlling the temperature of the injection molding cylinder, the start of plasticization is set as time point Z _and the end of the mold opening movement is set as time point Z ₂ .

Preferably, the time points Z 1 and Z 2 are determined by the same machine control pulse, the time point Z ₂ being the same as the time point Z for the next cycle.

Preferably, the temperature measuring location is located in the region of the geometric center between the contour of the compact and the temperature-regulating surface formed by the flow of the thermostating medium and in the region of the center between the inlet and outlet of the temperature-regulating medium, spaced from the contour of the compact.

Preferably, the temperature measuring location is located in the area of the geometric center between the mold wall and the temperature-regulating surface formed by the flow of the thermostating medium and in the area of the center between the inlet and outlet of the temperature-regulating medium, spaced from the contour of the compact.

Preferably, the temperature measuring point is located in the area of the geometric center between the outer and inner wall of the cylinder, in the middle area between the inlet and outlet of the temperature-regulating medium of the circuit concerned.

Preferably, the initial thermal equilibrium of the process is achieved by the following process steps:

- in the first cycle of the process, to the time point Z, -impulse t, _rivet is introduced at a fixed time to cause a first, full flushing of the temperature control circuit

- in the following cycles, the relative temperature control time t _d , depending on the desired thermal level, is divided into a certain number of initial pulses of different duration in the cycle, according to the following relationship td-anf = j ^ where:

t _d - relative temperature control time j - number from 1 to mm - number of values from 5 to K) for the thermal level, where 5 is the low thermal level and K) is the high thermal level, with only one input per cycle start pulse, and the determined start pulses are introduced as often until the previously entered value t _d is reached,

- when the value of td is reached, the integral WRG (Z ,, td) of the temperature course for that cycle is calculated and stored,

178 383

- in the next cycle after the cycle in which the value of td was reached for the first time, the WRG integral (Z _b td) is calculated from the temperature course and compared with the stored, calculated value of this integral from the previous cycle, and if the difference is smaller than the entered value in g, then this cycle is determined and stored as the reference cycle, and if the difference is equal to or greater than this value WRG (Z _b td), then the calculation of the integral with the value from the previous cycle is repeated in the following cycles, until the Wg value is exceeded and the start-up process is terminated.

Preferably, the method has additional steps during stationary operation in all cycles:

- start of temperature control at time point Z] of each cycle with the relative duration of temperature control td,

- temperature measurement of the supply stream and the exhaust stream continuously over successive and shorter time intervals,

- calculation of the WRG integral (ti. _ls> t,),

- comparing the calculated integral with the reference cycle integral at an identical point in the cycle,

- adjustments to the duration of the temperature control td in the current cycle based on a continuously determined difference.

Preferably, during the start-up phase when entering a setpoint temperature which is lower than the specified actual temperature, the temperature is continuously regulated at all subsequent time points Z _I and Z ₂ until the measured actual temperature for the first time has downwardly exceeded the entered setpoint temperature, with after lowering the set temperature, the initial phase continues by introducing the temperature control pulse tan at time point Z, the cycle following the first downward violation, and ends when the set temperature is exceeded again and the reference cycle is selected later.

Preferably, additional heat is turned on and turned off when the desired thermal level is reached.

Preferably, additional heating is activated before the start phase, either during the start phase or during the stationary operating phase.

The solution according to the invention was based on the following ideas: the enthalpy of the mold cylinder or plasticizing cylinder is determined from the heat supply components (amount of heat of the molten material injected, heating channel temperature control, etc.) and heat removal components (cooling the mold cylinder or plasticizing cylinder, heat removal by convection) and radiation, heat conduction). If the thermal operating state of the mold or plasticizing cylinder is to be kept constant during injection molding, it is necessary to compensate for the inevitable in the production process fluctuations in the individual enthalpy-determining components in their effect on the thermal operating state, e.g. of the mold. In order to remove heat from the mold, it is only possible to cool or regulate the temperature of the mold, and in particular, it is necessary to control the flow time of the temperature-regulating medium in the tool in such a way as to compensate for all kinds of disturbances that affect the enthalpy of the mold, such as changes in the temperature of the melt, fluctuations in temperature and volume of the flow of the temperature-regulating medium, variations in the cycle time, fluctuations in the ambient temperature, etc.

The explanations below refer to the variants of the mold temperature or cylinder temperature measurement.

The temperature control process is divided into two phases, the initial phase and the stationary operation phase, each with different temperature control conditions. Temperature control pulses for each cycle, especially in the state of the work phase, are always introduced at the time Z _b which is determined by a signal from the machine control unit, temporarily close to the operation and injection during mold temperature control, or temporarily close to the plasticizing operation, the beginning of the screw rotation at adjusting the temperature of the plasticizing cylinders so that at the time of the greatest temperature difference between the injected molten material and the channel

178 383 temperature regulators cause the necessary heat dissipation. At the latest time Z2, each temperature control process in the cycle ends, time Z2 being determined by a signal from the machine control which is triggered at a predetermined time near the end of the cycle. Throughout the cycle, the average mold temperature is continuously measured at the equally thermally loaded point for a given temperature control circuit, both from the molten material injected and from the temperature control side, this point approximately at the geometric center between the mold contour and a cooling channel or surface in the center area between the cooling water inlet and the outlet, at a sufficiently large distance from the mold contour, or when regulating the cylinder temperature in the geometric center area between the inner wall of the cylinder and the temperature control channel. After reaching or exceeding the predetermined set temperature of the mold for the first time, in accordance with the procedure that will be described later, the so-called reference cycle, whereby the start phase ends. The enthalpy in this reference cycle generally serves as the setpoint for the enthalpy of all subsequent cycles.

As a reference value for the enthalpy of the form depending on the time interval in the cycle, the WRG (u _b u2> according to the formula (1) was introduced.

at ₂

WRG (u1, u2) = J T (t) dt (1)

Ul

WRG (u1, u2) is defined and calculated as the integral of the temperature curve T (t) over the time axis between the time points u and u ₂ , where, u and u2 denote the time interval limit.

First, the WRG (Z _b t _D ) is calculated for the selected reference cycle, where t _D is the temperature control time calculated for the reference cycle.

Z1 + tD

WRGref (Z1, tD) = J T (t) dt Zl

In all subsequent cycles, at the time point Z _{x of} each cycle, the temperature control impulse starts the time tD, where tD is during each cycle and, in the event of deviations of the temperature course from the temperature course of the reference cycle, corrected as an object of the correction process, which will be described later. For this purpose, each next cycle starting from time point Z to the end of temperature control tD is divided into the smallest possible time intervals (t ^. _B tj), wherein at each time point temperature is measured and the calculated heat value WRGi _S / t ^. ₁ , t _I ) according to formula (1).

t;

WRGisit. ^ T,) ^ J T (t) dt h-1

WRG _I ,. _t (t _I lj, t,) is constantly compared at each time point t until the temperature control time tD has elapsed with the WRG value _re e {t, ll, t,) of the reference cycle, always at the same cycle time point according to the formula ( 2).

WD (t) = WRG, st (ti.1, t ₎ ) -WRGref (ti- _b t,) (2)

The difference between the two values WD (t1) signals the differences in the amount of heat removed from the mold in this time interval (t1, t1 and is used according to the invention to correct the temperature control time tD for the correction time t _konr ( _t1 ).

For the results calculated according to formula (2), the following distinction applies:

178 383

WD (t)> 0: compared with the cyclically equal time interval of the reference cycle, the mold enthalpy in the current cycle is greater, and the temperature control time must be extended by the value of t _end (t,).

WD (t1) <0: compared to the cyclically equal time interval of the reference cycle, the mold enthalpy in the current cycle is smaller, and the temperature control time must be shortened by the value of t _corr (t,).

WD (ie) = 0: no need for temperature control time correction.

To calculate the value of t _corr (t ₁ ), the following considerations are made:

Let us assume the existence of the case WD (t)> 0. The time tkor- (t) needed to discharge the excess value proportional to the amount of heat calculated according to formula (2) is added up at the time point, i.e. with the set temperature control time t _D.

Therefore, tD0i) - tp0i-l) + tkorr (ti) applies, where tkorr (ti) should be derived from the following relationship:

^ D0i- 1) ⁺ weapon (* i)

WD (ti) = J TE (t) dt ^ D0i1) where TE (t) is understood as the temperature unit for which the following applies:

TE (t) - 1 for t> 0 (3)

Therefore ^ 01- l) + tkorr 0i) applies

WRGist 0i— I »0) - WRG _re f 0i— 1> M) ⁼ J TE (t) dt

0i- i) * i ^Ι ϋ0ι-l) ^{+ t} korr0i)

JT (t) _ist dt- JT (t) _ref dt = jTE (t) dt) * i- 1 Li ^ D0i-l)

After inserting the value of time and assuming that the lengths of the time interval approach zero and the values Ttt, _j) tend to the value of T (t,), we get

T (t,), st * (t ₁ -ti-1) -T (t _l ) _r ef * (t, -ti-1) = TE (to) ref * (tD + W fe) (T (t ,), _sr T (t ₁ 1ref) * (t _r t, -i) = TE (tD) ref * 0korr) and therefore is ^ ΟΓΓ0ΐ) ~ (T0i) ist T0i) ref) * 0i ^t i1) and after taking into account (3)

TE 0D) ref tkorr (t,) - (T (ti) i _S t - T (t _t ) _re f) * (t ^ ti.1) (4) where:

t is a separate time point for measuring the mold temperature

178 383

T (t) is the mold temperature

Q _{) St} means that the factor relates to the current cycle

0 _r ef means that the factor relates to the reference cycle t _D means the temperature control time in the cycle.

For applications where due to external circumstances, for example, mold layout unfavorable in terms of temperature control, exhibit excessive inertia of heat transfer from the molten material to the temperature-controlling medium, the factor K in the range of 0.2-1 is introduced into formula (4), 0, which if necessary acts as a damping for the calculated correction time t _kmr ( _t1 ). You get then:

tkorr (ti) = K * (T (ti) i _S t - T (t |) _re f) * (trti-1)

For the case of WD (t,) <0, the same derivation is obtained for tkorr (ti), respectively, with the correction time t _corr (ie) having a negative sign.

In the initial phase of the first cycle, starting at the time point Z _{E, there} is an initial pulse t _mit with a set time to obtain the first complete rinse of the given temperature control circuit, and when a certain interval of the average mold temperature from the specified temperature in the next cycle is reached at the point In time Z1, a temperature control pulse tann is introduced with a shorter time, the temperature control pulse tn1 being introduced in all subsequent cycles until the first predetermined set temperature is exceeded and ensures the damped approach of the average mold temperature to the selected set temperature.

A variant occurring as a special case in the initial phase consists in the fact that when entering the set temperature, which is lower than the measured real temperature, in all subsequent cycles between the time points Z and Z2, the temperature control takes place until the measured real temperature for the first time drops downwards. the entered setpoint temperature. After the set temperature is exceeded downwards, the initial phase with the introduction of the coolant impulse extends the time t ^ n up to the time point Z1 of the cycle following the first violation downwards, and ends when the set temperature is exceeded again and the reference cycle is selected later.

After the predetermined setpoint temperature has been exceeded, the plasticizing mold or cylinder is guided with a calculated impulse of the temperature regulating medium updated in each feed cycle and a temperature control phase depending on the current comparison of the setpoint and the actual value over a number of n cycles to thermal equilibrium. For this purpose, the arithmetic mean of the cooling time of the first cycle is determined from the entire duration of the impulses of the temperature-regulating medium in a fixed number of immediately preceding cycles, evaluated by the factor K _b, which allows reacting to the practically unavoidable occurrence of thermal disturbances in the temperature state of the mold, and as the calculated pulse time t _E is used to introduce the temperature control medium into the next cycle at time point Z _E

After the input of the impulse of the temperature-regulating medium with time t _E , as a result of the continuous comparison of the set value with the actual value of the mold temperature for the duration of each upward violation of the set temperature, and thus depending on the temperature at the latest at time Z _{2 of the} current cycle, further pulses of the temperature-regulating medium.

The time t _{E of} this impulse is determined by the formula n (5) _tE = mi _{ftEi + tvi)} i = l

178 383 where:

n - set minimum number of consecutive cycles from the first overrun to the top of the entered set temperature of the mold to finding the thermal equilibrium, t _E i - temperature control pulse calculated for the cycle izn cycles, ty, - sum of temperature-dependent temperature control pulses of the cycle and zn cycles , j - the number of cycles after the first time the set temperature is exceeded, and Kl (j) - a value dependent on j, depending on the machine and the method, which is used to estimate the average temperature control time from n cycles.

For the calculation, the following initial conditions apply from the first cycle after the set temperature is first exceeded:

(*) Eli ~ tann (**) Obtaining (5) follows for j <n, with n being followed by j.

(***) Kljj) -: o + ^a i *) for.) <N

Kl (j) = 1 dlaj = n

If the set number of n cycles is reached after the first entered set temperature is exceeded, then at the time point Z, the reference cycle, a temperature control pulse is triggered with the time t _D , where t _D is equal to the value t _E calculated in the nth cycle according to (5) and the heat value WRG _re e (Z1, tD) is calculated.

In the next cycle, the temperature is controlled again at time tD and the described temperature integral is calculated. If the difference of the two integrals is less than the entered value W _o , then the last cycle is designated as the reference cycle, the temperature progression in the mold is appropriately maintained, and the initial phase is considered complete. For Wo, a value from 0.1 to 5%, preferably 2%, calculated as the reference of the integral WRG (Z, tD), is entered. If the difference of the two integrals is greater than the entered value of Wo, then, starting at j = 1, n cycles follow the described operating mode again to report finding, with n preferably being selected as three, and Kl (j) = 0.75. Again, temperature control pulses can be triggered by comparing the actual value with the set value. After each of the three cycles, the temperature control time t _E is calculated for the next cycle according to (5). After the third cycle, Kl (j) = 1 and tD = tE is determined, the temperature control impulse with time tD is triggered and the integral of the heat value WRG (Z _b tD) is calculated. Triggering an impulse and computing the integral values to be compared with the previous cycle, and making the reference selection described, starting with j = 1, causes the integral computation to be repeated in the next cycle as well, until the condition is met:

WRGj., (Z1, t _D ) -WRGj (Z _b tD) <Acc

The current cycle is marked as the reference cycle and the start phase is closed. Already before the first cycle of the machine, additional heating can be added, which reduces the heating time to the required thermal level in the temperature control circuits relating to the thermal operating state or in the cylinder zones important for the thermal operating state of the plasticized mass. When using additional heating, it is turned off at a set distance between the mold or cylinder temperature and the set temperature.

Regarding the signals from the machine control unit, which are related to the time points Z _t and Z 2, the following possibilities are used to control the mold temperature of the object.

As time point Z _x , the start of the post-pressurization time is selected, and as time point Zj, the end of the mold opening movement is selected, or the beginning of the injection operation is selected as the time point Z1, and the end of the mold opening movement as Z2, or the time point Z1 and the time point Z _{2 are} determined by identical signals from the machine control, Z ₂ in this case being identical to the next cycle signal Z. The latter case is preferably used at a relatively low desired mold temperature.

178 383

In the case of cylinder temperature control, the time point e _x is, for example, the start of plasticization, and for the point Z2, the same variants are used as for the mold temperature control.

The statements below refer to the variants where the temperature of the exhausted medium is measured.

As the value related to the enthalpy of the form depending on the time interval in the cycle, the WRG (u, u ₂ ) is entered according to the formula (Γ).

at ₂

WRG (UI, U ₂ ) = J (Tfueck (t) 'T _VO r (t)) dt (1) ^u i

WRG (ui, u ₂ ) is defined and calculated in the same way as the integral of the temperature curve over the time axis between the time points ui and u ₂ , reduced by the integral of the temperature course of the medium exhausted in the same time interval, where T "eck (t) is the course temperature of the exhausted medium, t _vor (t) is the course of the temperature of the supply medium, and au, iu ₂ are the limits of the integration time interval. Possible time of heat dissipation from the mold between the time points Zr determined by the signal from the machine control unit near the injection operation when regulating the mold temperature, or near the beginning of plasticization when regulating the cylinder temperature, and between the time points Z ₂ determined by the signal from the control unit operation of the machine near the end of the cycle, it is entered from zero (maximum heat dissipation) to 100 (minimum heat dissipation) by percentage, but inversely with respect to the possible temperature control time. The operator specifies the desired time of heat dissipation as a percentage of a given partition, i.e. as a relative temperature control time. In the first cycle, designated as the reference cycle, after reaching the thermal equilibrium of the form, the value of WRG _re fZi t _d ) resulting from the introduced relative temperature control time t _d is calculated as follows.

t _d

Gref (Zi, td) - J (Tmeck (t) ~ Tyor (t)) dt ^Z 1

In all subsequent cycles, at the time point Zr of a given cycle, the temperature control impulse starts with the time td, where td as the object of the correction method, which will be described later, is corrected during the given cycle and with the occurring deviations of the temperature course in relation to the temperature course of the so-called cycle reference. For this purpose, each subsequent cycle, starting from the time point Zr up to the end of the relative temperature control time td, is divided into the smallest possible time intervals (t, _b Q, at each time point t, the temperature of the feed and exhausted medium is measured and the temperature of the exhausted medium is measured. is the value of WRO ^ Ct ^ -t) according to the following calculation formula:

t

WRG.stC.-Bt ^ J (TrueckCO-Wtjjdt V.

The heat value WR ^ sCj ,, Γ) is constant for each time point t, and until the relative temperature control time td has elapsed, it is compared with the value WRG _re f (t, "tr of the reference cycle, always at the same time point cyclically according to the formula (2 '):

WD (ti) = WRG, ss 1,1, t) -WRGref (t, i, t,) (22)

178 383

The difference of the two values signals the difference in the amount of heat discharged over the time interval (t, _b t ₁ ) from the mold and is, according to the method of the present invention, used to correct the relative temperature control time td for the correction time t _end (i.e.) in the current cycle.

For the results calculated according to formula (2 '), the following differentiation of cases applies:

WD (t)> 0: compared to the cyclically equal time interval of the reference cycle, the mold enthalpy in the current cycle is greater, and the temperature control time must be extended by the value of t _kort (t,).

WD (t ₁ ) <0: compared to the same cyclic time interval of the reference cycle, the mold enthalpy in the current cycle is smaller, and the temperature control time must be shortened by the value of tkord

WD (ie) = 0: no need for temperature control time correction.

When calculating the value of ^ (0, the following premises can be derived:

In general, the case WD (T,)> 0 applies without limitation. The time tk _Orr (t,) for the discharge proportional to the amount of excess heat calculated according to formula (2 ') is at time t, added to the entered relative temperature control time td .

The following applies to td td + tkorr0i) where t _to r should be derived from the following relationship:

WD (t,) = WRCiref (td, td + tkorr) where applicable

WRGistOi-h t,) -W / RGref (ti- ,, t,) - WRGref (td, td + tkorr) and

J (Trueck (0 T _vor (t)) j _s ^ dt J 04 ^^ 0) - T _vor 0)) _re f dt - J (Tp ^^ t) - T _vor 0)) _re f dt

L = i b-1 t _d

After inserting the value of time and assuming that the length of the time interval tends to zero, so the values of !ί.,) Tend to the value of T (i.e.) we get

TruecC0) -Tvoo (ti)) Ist1j0Γtltl) - (Tuιeck0I) -Tvor0i)) ref * (t | -ti-l) = (T (td) -Tyor (td)) ref * (td + 'tkon - d) ((Trueck (t,) - Tvor 0,)) isr (Trueck0i) 'Tvor0i)) ref) * (tl-ti-n) - (T0d) -Tvor0d)) ref * (tkorr) and therefore _t ((Trueck0i) ~ T _VO r 0j)) jst ~ (Trueck (M) ~ Tyo _r 0i)) ref) * fli- l) (T0 _d ) - T _vor (tj)) _re f where:

t, separate time point for measuring the temperature of the return medium (exhausted) Tmeck (t) temperature of the return medium,

T _V or (t) temperature of the supply medium,

178 383

() _ist · factor related to the current cycle,

() ref • factor related to the reference cycle, td time of cycle temperature control.

For applications which, due to external circumstances, for example unfavorable thermal and technical layout of the mold, show excessive inertia of heat transfer from the molten material to the temperature-regulating medium, the factor K from 0.5 to 1.5 is introduced into formula (3), which, if necessary, acts to dampen or amplify the calculated correction time t _corr (ti). You get then:

_ " _T ((Trueckfti) - ^ yorOi ^ ist ~ (^ rueckOi) ^- TyorOOKef) * (* i ~ tj- l) k ^Qrr (T (td) - T _V or Od)) ref

For the case WD (t,)> 0, the same derivation is obtained for tko-rOj, with the correction time t _kOT r (t _i ) being negative.

The actual temperature control process is divided into two phases, an inception phase and a stationary operating phase, each with different temperature control conditions, the inception phase ending when the reference cycle is selected. Temperature control pulses are always introduced at a point in time close to the injection or plasticizing operation, at the beginning of the screw rotation, so that in the time range of the greatest temperature difference between the injected melt or plasticized mass and the temperature control channel, the necessary heat dissipation occurs. The duration of the pulse during the start-up phase is here determined by the initial operating mode, during which it is entered in the stationary operating phase as the relative temperature control time, and as a result of the above-described correction method is constantly adapted to the requirements of the production process. The temperature control in the cycle ends at time Z ₂ at the latest.

Already before the first cycle of the machine, the method according to the invention makes it possible to connect additional heating, which in the temperature control circuits relating to the thermal operating condition or in the cylinder zones important for the thermal operating condition of the plasticized mass minimizes the duration of heating to the required thermal level. When additional heating is used, it is turned off after the duration that determines the pulse regulating the temperature in accordance with the set temperature increase of the medium return.

In the initial phase of the first cycle, starting at the time point Z ₁ , the temperature is initially controlled by a pulse t _m i "at a specified time to achieve a first complete flushing of the concerned control circuit. In the following cycles, the entered relative time td is divided into initial pulses, the duration of which is determined from the formula, depending on the thermal level required in the form.

td td-anf - j * m

wherein j varies from 1 to m, and preferably m = 5 is for the desired relatively low thermal level and m = 10 for the desired relatively high thermal level. After reaching the set value of the relative temperature control time, the described integral WRG (Z _b td) of the temperature course is calculated for the first time for this cycle. The next cycle is treated as the reference cycle, the temperature is regulated with the given relative duration and the described integral is calculated again. If the difference between the two integrals is less than the set value of Wg, the last cycle is considered as the reference cycle, the temperature course in the flow and outflow of the medium is properly maintained and the initial phase is considered complete. For WG, a value of 1-20%, preferably 10%, of the integral WRG (Z _b td) calculated as reference is entered. If the difference of both integrals is greater than the entered value of Wg, the temperature is re-controlled with a given relative duration and compared with the calculated value of WRG (Z _b i.e. of the previous cycle. This sequence of temperature control i

178 383 comparing the integrals continues for each subsequent cycle until a level below the set point W _G and the associated designation of the current cycle as the reference cycle and zakończema initial phase.

The reference cycle is the cycle after the thermal equilibrium of the assembly, e.g. cylinder or mold, is reached. As exhaustively described, this state of equilibrium is achieved by the mentioned process steps in the initial phase. Thermal equilibrium can also be achieved in other ways. As for the signals from the machine control which are related to the time points Z _x and Z ₂ , the following possibilities exist for controlling the mold temperature, for example.

The start of the post-pressurization time is set as time point Z _x , and as time point Z2, the end of the mold opening movement or the time point Z, the start of the injection operation, and as Z _{2 the} end of the mold opening movement, or time point Z1 and time point Z ₂ are determined by identical signals from the machine control, in which case Z2 is identical to the next cycle signal Z _x . The latter case is preferably used with a relatively low desired mold temperature condition.

For the cylinder temperature control as time point Z, for example, the beginning of plasticization is determined, and for time point Z2 the same variants apply as for mold temperature control.

Due to the temperature control method according to the invention, the process stability in injection molding is significantly increased. The scrap percentage can be reduced by approximately 30% compared to conventional temperature control methods. A cycle time reduction of about 5% leads to a noticeable increase in the efficiency of p ^ ioldulcc ^ yjjr ^ <jj. External temperature control units with heating and circulation pumps are only needed when high temperatures of the temperature control media are required. As a result, the specific energy consumption of the injection molding process is reduced by approximately 10%.

The additional advantage is that the temperature control on the basis of the temperature of the feed and return medium is that it is not possible to introduce thermal sensors into the cylinder wall or into the injection mold. Particularly with complex injection molds, the insertion of holes for the thermal sensors is associated with a considerable expense.

A further advantage also lies in the fact that in injection molding machines it is possible to carry out the temperature control according to the invention for both the injection mold and the cylinder. Both technological sequences can therefore be coupled with each other in a common control device, thanks to which the costs of the equipment are significantly reduced.

The invention is illustrated by the drawing, in which Fig. 1 shows a diagram of the injection mold temperature control with the measurement of the return medium temperature, and Fig. 2 shows a temperature control diagram of the injection molding machine cylinder with the measurement of the return medium temperature (exhausted).

1 shows an injection molding machine 1 with an injection mold 2. Temperature control of the injection mold 2 is carried out by circuits K into the temperature-regulating medium, the flow of this medium being interrupted or released for each circuit by means of solenoid valves M1 for

2 shows an injection molding machine 1 with a plasticizing cylinder 2 '. The temperature control of the plasticizing cylinder 2 'is carried out by the temperature control circuits K, to Kn, whereby the flow of the temperature control medium for each temperature control object can be interrupted or released by means of the solenoid valves M1 to Mn. The thermal operating state of the cylinder zones, which are assigned to the temperature control circuits K.1 to Kn, can be increased by the heating circuits H to Hn to the preset temperature level. and when the heat dissipated from plasticization is exclusively used, additional heating can be dispensed with.

The inventive control device 3 for regulating the temperature of the mold or plasticizing cylinder is composed of an conformation stage, an analog-to-digital converter (ADU), a computer unit (CPU), an input unit, an output unit, and various interfaces. The functional relationship of the individual units in this device, and thus in the injection molding or plasticizing process system, temperature measurement and flow matching of the temperature control medium, is as follows: for each control circuit K, (i = 1, ... n) of the injection mold or plasticizing cylinder in A thermal sensor ThR (i = 1, ... n) is arranged in the vicinity of the mold or cylinder to the returning temperature control medium, which is flexibly connected to the degree of fit of the control device. Additionally, a ThV thermal sensor is placed in the supply of the temperature-regulating medium.

By means of the matching stage, the thermal signals are matched to the selected sensors and transmission materials on the connected analog-to-digital converter (ADU). It transfers the received thermal signals in the form of electrical signals to a computer unit (CPU), where they are processed. The software installed in the CPU, starting from the integral of the temperature course in the selected reference cycle, from the temperature course measured synchronously to the cycle in each subsequent cycle, and from the integral of the comparison calculated on this basis, determines the flow time of the medium regulating the temperature in a given cycle.

The beginning and end of flow of the temperature control medium are determined by the CPU by generating switching signals to the solenoid valve of the respective temperature control circuit. Measured values, computer results and temperature control circuits can be assigned. Also connected to the CPU are a setpoint input and output for user guidance. The signals Z1 Z2 inputted to the CPU from the injection molding machine control provide a time reference for the injection molding process.

The operating diagrams for variants of temperature measurement in the injection mold or in the cylinder wall of the injection-molding machine are essentially of the same design, except that the thermocouples are not placed in the return medium, but in the cylinder wall or in the injection mold. The measurement site should preferably be located in the area of the geometric center between the mold contour and the channel or cooling surface and in the area of the center between the inlet and outlet of the temperature-regulating medium.

Examples of the method according to the invention are given below. Examples 1-3 relate to the embodiment with measurement of the temperature of the return medium, and Examples 4-6 relate to the embodiment with measurement of the mold temperature or the cylinder wall temperature.

Example 1.

On a Krauss Maffei 150-620 B injection molding machine, the automotive part of the engine ventilator is produced from polyamide 6.6. The technical parameters are as follows:

Layout of the form double Injection weight (in moldings + riser 204 g Mold weight: 850 leg Injection pressure 920 bar Injection time 18 pp Closing force 1300 In Pressing 750bru Press-in time 5.5 seconds Supply temperature 37 ° C Cycle time 33 pp The injection system has four temperature control circuits, a temperature sensor in the return

each circuit and a sensor on the supply line for temperature control in conjunction with the control unit. The start of excess pressure was selected as time point Z1 and the end of the mold opening movement was selected as time point Z2. The time between Z1 and Z2 is 22 seconds.

The relative temperature control time t _d for circuits 1 and 2 (nozzle side) was set to 50%, i.e. 11 s, and for circuits 3 and 4 (motion side) 40%, i.e. 13.2 s.

178 383

The return temperatures of the medium regulating the temperature of the respective circuits are measured directly at the exit from the mold. Temperature measurements of the supply and exhaust medium are carried out continuously throughout the cycle.

The sequence of the method will be explained using the example of the temperature control circuit 1. In the start phase of the first cycle, starting at time point Z ", an initial pulse is given at a predetermined time to obtain the first complete rinsing of the control circuit concerned. The time of the initial pulse t _init is determined empirically from the existing experimental values. 5 s is considered sufficient for this example. For each of the following m cycles, the initial pulse is determined as follows:

td-anf ~ j * m

This calculation is performed depending on the cooling circuit, selecting m = 5. For circuit 1, cycles 2-6 will generate the following temperature control pulses: 2.2 s, 4.4 s, 6.6 s, 8.8 s , 11 pp.

After reaching a certain value of the relative temperature control time, i.e. 50% or 11 s, for this cycle the described integral WRG (Z _b t. _(I ) from the temperature course WRGj (Z _b t _d ) = 27.5 is calculated for the first time. The next cycle is treated as the reference cycle, the temperature is regulated for a given 11 s, and then the described temperature integral is recalculated WRG (Z _b td) = 28.3. The difference between these two integrals (0.8) is smaller than the entered value Wo (2). , 75), which means that the last cycle run is considered as the reference cycle, the time history of the feed and return (exhaust) medium temperature is stored and the initial phase is considered to be closed.

In all subsequent cycles, at the time point Z1 of a given cycle, the temperature control impulse begins with the time td, where td (11 s) is corrected using the correction method during a given cycle and with the occurring deviations of the temperature course in relation to the temperature course, the so-called reference cycle. For this, each successive cycle, starting from time point Z _b up to the end of the relative temperature control time td, is divided into the smallest time intervals (ti, (,) with a duration of 0.05 s, the temperature is measured at each time point t. exhausted medium and the value of WRGi _S t (t _N , t) is calculated according to (1):

t

WRG, st (ti-i, t,) = J (TnKckW-TyorWjdt E-1

WRGis (ti.1,1 is constantly compared for each time point ti until the end of the relative temperature control time d with the value WRG _ref (ti-1> t) of the reference cycle and always at the cyclically equal time point according to (2). Difference WD (t) of these two values is according to the method of the invention used in the current cycle to correct the relative temperature control duration _td by the correction time ^ ¢ 1.

WD (tO - WRGist (ti-1, t1) -WRGrel (ti-1, t,) _{t =} K (CE-ueckfti) Fyor (ie) j _s t ~ (^ riiecikOi) —T _vor (ie)) _re f) * (t ^ _ j) (T (td) -Tvor (td »ref where K = 1 applies.

From the measurement results and computer results in the table below, for example, the values of T _ni e _Ck (t ₁ ), T ^ / t,), WRG _lst (t, -i, t), Wd (U ^ _οπ (Ό and td for Measuring points 50, 80, 120, and 200 of the 20th cycle of the temperature control circuit 1.

178 383

Time point Trueck T _V or WRG, p WD tkorr td and in t (° C) in t (° C) Tue Tue Tue (s) Tue (s) 50 41.6 37.0 0.24 -0.01 -0.04 10.1 80 40.8 37.1 0.185 -0.02 -0.04 9.4 120 39.7 37.0 0.135 0.005 0.01 9.7 200 38.1 37.0 0.06 0.01 0.02 10.6

All temperature control circuits are supplied with domestic hot water from the plant's closed cooling water network, which has an inlet temperature of 37 ° C. The use of a temperature regulating device is not necessary.

According to the process of the present invention, the initially mentioned compacts were continuously produced in good quality within a cycle time of 33 seconds. The specified scrap percentage was 2.6% and the specific energy consumption was 0.59 kWh / kg.

Example 2

On a Krauss Maffei 250-1200 B injection molding machine, a cover is made of polypropylene filled with 40% talcum powder.

The technical parameters are as follows: Layout of the form poemincza Weight of one injection (2 moldings + riser) 210 g Mold weight 770kg Injection pressure 800 bar Injection time 2.0 s Closing force 2000 IN Pressing 700bar Press-in time 3.5 seconds Supply temperature 14 ° C Cycle time 26.5 s The injection mold is equipped with four temperature control circuits, a temperature sensor

the return pipes of each circuit and a sensor in the inlet of the temperature-regulating medium in conjunction with the control unit. The start of set pressure is selected as time point Z1 and the end of the mold opening stroke is selected as time point Z ₂ . The time between points Z1 and Z ₂ is 19 seconds.

The relative temperature control time t _d was set for the temperature control circuits 1 and 2 (nozzle side) 70%, i.e. 5.7 s, and for the circuits 3 and 4 (motion side) 65%, i.e. 6.6 s.

The medium return temperatures of the respective temperature control circuits are measured directly at the exit of the mold.

The downstream and upstream temperature measurements are performed continuously throughout the cycle.

The course of the process is analogous to that in Example 1, where m = 5 is set for the calculation of the initial pulse time, and the initial phase ends after seven cycles by selecting the reference cycle. The temperature control pulses calculated in the next cycles have a duration of 4.2 s to 7.5 s for circuits 1 and 2 and from 5.4 s to 8.0 s for circuits 3 and 4 under the influence of practically occurring thermal disturbances of the mold operation condition. .

All temperature control circuits are supplied with domestic hot water from the plant's closed cooling water network, the inlet temperature being around 14 ° C. The use of a temperature regulating device is not necessary.

According to the method according to the present invention, during one working day in three-shift operation, the previously mentioned moldings were produced of good quality, obtained thanks to the achieved thermal stability of the operating condition with optimal process stability over time.

178,383 cycle of 26.5 s. The specified percentage of scrap was 0.85% and the specific energy consumption was 0.55 kWh / kg.

Example 3

Manufacture of shock-absorbing buffer sections from a rubber mixture based on SBR / NR rubber by injection molding. The technical parameters are as follows:

Injection molding machine: - Closing force of 850 kN

- Diameter of the worm piston 45 mm

- Screw rotation speed 90 rpm.

- Back pressure in percent 35%

- Cycle time 45 s

Mold: - fully automatic demoulding

- electrically heated

Molded part: - open, directly injected by the spreader system

- Number of elements 44

- Injection weight (including riser) 0.064 kg

The plasticizing cylinder is equipped with three temperature control circuits which are coupled to the control unit via thermal sensors in the medium return and via a thermal sensor in the medium supply. Circuit 1 (ground input) and circuit 3 (nozzle area) have additional heating. The start of plasticization is selected as time point Z1 and the end of the mold opening movement is selected as time point Z2. The time between Z1 and Z2 is 37 seconds.

The relative temperature control time t _d was set to 90% (3.7 s) for circuit 1 (insertion zone), i.e. a relatively high level of frictional heat should be maintained, and for circuits 2 (start of the ejection phase) and 3, 80% ( 7.4 s). For the thermal operating state of the plasticizing cylinder, these set parameters represent the enthalpy increasing in the cylinder towards the ejection zone, which results from the frictional heat relatively strongly increasing in this direction. The return temperatures of the temperature-regulating medium of the respective circuits are measured directly at the cylinder outlet.

The return and feed temperature measurements are performed continuously for the entire duration of the cycle.

In the initial phase, after a few minutes, such a level of thermal operating status is reached that the additional heating can be turned off. The starting phase is complete after 12 cycles, with 3 cycles being used to establish the reference cycle. Impulses of temperature control calculated in the next cycles reach the duration of 2.0 - 5.5 s for the circuit 1 and 5.4 s - 8.6 s for the circuits 2 and 3 under the influence of factors disturbing the thermal operating state of the plasticizing cylinder. ^^ i ^ j ^ ii temperature control rsi ^ m ^ These are utility water from the closed cooling water network of the plant, which has an inlet temperature of about 14 ° C. The use of a temperature control device is not necessary.

According to the method of the present invention, the already mentioned high-quality moldings were produced in continuous operation with the following parameters:

- Cycle time 45 s

- Scrap rate 2.9%

- Specific energy consumption 0.60 kWh / k.g

- Additional maintenance effort for 22 min. regulatory work in one shift.

Example 4.

On an injection molding machine type Krauss Maffei 150-620 B, the automotive part was produced with the engine vent from polyamide 6.6. The technical parameters are as follows:

- Form layout

- Injection weight

- Mold weight

- Injection pressure

- Injection time

- Closing force double grazing + 20 (^ 4 gnadle)

850 kg

920 bar

1.8 seconds

1300 N

178 383

- Holding pressure

- Holding time

- Inlet temperature

- Cycle time

750 bar

5.5 s 37 ° C 33 s

The mold is equipped with four temperature control circuits, which are coupled with the control unit through temperature sensors. As the set temperature T _{soll of the} mold, 65 ° C was entered for the temperature regulating circuits 1 and 2 (nozzle side), and 55 ° C for the circuits 3 and 4 (motion side).

The mold temperatures in the area of the temperature control circuits are measured in the geometric center between the channel and the mold contour and possibly in the center between the inlet and outlet of the temperature-regulating medium of the circuit in question.

Using the example of the temperature control circuit 1, the arrangement of the opening for the sensor will be described. In the center, between the inlet and outlet of the temperature-regulating medium, an opening is placed between the two channels running parallel to each other and with respect to the mold contour, at the geometric center between the two channels and perpendicular to the mold contour. The bore ends halfway between the channel and the mold contour, in front of the mold contour. The specific dimensions of the temperature control circuit 1 are as follows:

- Distance between the axes of both temperature control channels: 40 mm

- Distance between the center of the temperature control channel and the contour 40 mm

- Distance between the bottom of the hole and the contour 20 mm

The holes needed to measure the temperature in the temperature control circuits K ₂ , K3 and K4 are made in the same way as for the circuit 1.

Measurements are carried out continuously throughout the cycle. In response to the measured values, pulses of the temperature-regulating medium with a limited time are introduced into the respective cooling circuit.

In the first cycle of the start-up phase, starting at the time point (start of the boost pressure), a temperature control pulse t1 is triggered at a predetermined time, by means of which the first complete flushing of the given cooling circuit is achieved. The time of the initial pulse t. _Ni i is always determined empirically on the basis of existing experimental values, 5 s being considered sufficient for this example.

In the next cycle, when a certain distance between the measured average mold temperature and the entered set temperature of 3 K is reached, in the temperature control circuits at the time point (start of the pressure addition), the tan _n pulse is introduced for 0.3 s. This 0.3 s pulse is introduced in all subsequent cycles, until the first entered set temperature is exceeded. When the set temperature is reached or exceeded, the search for thermal equilibrium in the mold begins.

Wn = 5 cycles, after the first set temperature is reached or exceeded at the time point Z1, the average temperature control pulse t _E is entered, which is calculated as the average value of the total cooling time of the previous five cycles using the K1 factor according to the following formula:

n

i = 1 where n = 5, where for K1 (j) the following applies: K1 (j) - a ₀ + a1 * j for j <6 K1 (j) = 1 for j> 5

178 383

Taking into account the thermal inertia of the heat transfer processes at the beginning of the stationary phase of operation and the resulting often overshoot processes during temperature control for the a ₀ ia, constants, the following values were selected _o = 0.25; ar = 0.15;

For K 1 (j), a moaotoaiccaie is obtained, an increasing waveform depending on j, which ensures that only after the fifth cycle from exceeding the set temperature upwards, the calculated impulse has the time t _D needed to maintain the set temperature entered. The time t _D is equal to the value t _E calculated for the sixth cycle according to (5), in this example tD = 12.7 s.

The temperature control process is now established by equilibrium between the set temperature and the actual temperature.

For this, in this example, the sixth cycle, when the set temperature is exceeded for the first time, the described integral WRG (Z ,, tD), from the temperature course, WRG (Z ,, tD) = 820.9 is calculated. In the next cycle, the temperature control is performed again with the calculated time tD, and the described temperature integral is again calculated WRG (Z, tD) = 826.7. The difference of both these integrals (5,8) is smaller than the entered value W _G (W _G = 16,4), which means that the last cycle run is treated as a reference cycle, the time course of the temperature measured in the mold or in the cylinder is stored, and the initial phase is considered complete. In all subsequent cycles, at the time point Z1 of each cycle, the temperature control pulse with the time tD begins, where tD (12.7 s) is corrected using the correction method in the course of each cycle and with the occurrence of temperature variations in relation to the temperature course, the so-called odninsinain cycle. To this end, each subsequent cycle, starting from time point Z1 up to the end of the calculated temperature control time tD, is divided into the smallest possible time intervals (i.e. -, ie) with a duration of 0.05 s, at each time point t, the mold temperature is measured and the value of WRGisiti-, 1 is calculated according to (1).

t

WRGut (t, -i, t,) = J T (t) dt t, - 1

The value of WRGjsIi.,, T, is constantly at each time point t, and until the temperature control time t _D expires, it is compared with the value of WRG _re jt, i, i.e.) of the cycle runtime, always at the same time point in the cycle according to (2) . The difference WD (t,) of these two values is used to correct the temperature control time tD by the correction time t _corr (t,) in the current cycle.

WD (t,) = WRCMU t.) - WR ^ eiCH, t.) Tkon ^ (ti) = K * (T (ie) st (- T ^ OreT ^ t-t.-) with K = 1.

From the measurement results and from the results of computer calculations, for example, the values of T (t ₁ ) (ist), WRGjs (ti.1, t, 1, WD (ie), tk _O r (ie) and tD for the 1st, 50th, 80th The 1st, 120th and 200th test points of the 20th cycle of the temperature control circuit 1.

Time point i T _ls! Tue ( ^o C) T _re ewt WRGrefWt tkorr W tj (s) t _D after t (s) 1 64.8 64.8 3.25 0.00 12.7 50 65.8 66.3 3.30 -0.025 12.1 80 66.7 66.7 3.34 0.00 11.8 120 66.0 66.2 3.30 - 0.01 11.6 200 65.4 65.2 3.25 0.01 12.0

178 383

As can be seen from this example, the 12.7 s temperature control pulse entered in the reference cycle that was needed in the raise cycle to maintain the entered setpoint temperature during the 20th cycle is corrected from 12.7 to 12.1, 11.8 , 11.6 until 12.0 s.

All temperature control circuits are supplied with utility water from the plant's closed cooling water network, with an inlet temperature of 37 ° C. The use of a temperature regulating device is not necessary.

According to the method of the present invention, the aforementioned compacts were produced in continuous operation in good quality within a cycle time of 33 seconds. The scrap percentage was 2.6% and the specific energy consumption was 0.59 kWh / kg.

Example 5

On an injection molding machine type Krauss Maffei 250-1200 B, the car part was produced with a cover in polypropylene filled with 40% talc. The technical parameters are as follows:

- Form layout single - Injection weight (2 moldings + riser) 210 g - Mold weight 770 kg - Injection pressure 800 bar - Injection time 2.0 s - Closing force 2000 kN - Holding pressure 700 bar - Holding time 3.5 seconds - Inlet temperature 14 ° C - Cycle time 26.5 s The injection mold is equipped with four temperature control circuits, and the temperature sensors

The elements placed in the mold according to the method of the invention in the area of each circuit are coupled to a control unit. The start of pressurization was selected as time point Z1 and the end of the mold opening movement as time point Z2. The time between Z1 and Z2 is 19 s. The set temperatures for the temperature control circuits 1 and 2 (nozzle side) are 55 ° C, and for the circuits 3 and 4 (motion side 45 ° C).

The process is analogous to that of Example 1, with the start phase being completed after eight cycles.

The temperature control pulses calculated in the next cycles will reach 4.2 s - 7.5 s for circuits 12 and 5.4 s - 8.0 s for circuits 3 and 4, taking into account practically existing factors disturbing the thermal state of the mold operation.

All temperature control circuits are supplied with utility water from the closed cooling water network of the plant, the inlet temperature being around 14 ° C. The use of a temperature regulating device is not necessary.

According to the method according to the present invention, for one day in a 3-shift operation, the already mentioned moldings were produced of good quality and with optimal process stability due to the achieved stability of the thermal operating condition over a cycle time of 26.5 s. The percentage of defects was 0.85%, and the specific energy consumption was 0.55 kWh / kg.

Example 6

Manufacture of a shock absorber bumper profile from a rubber compound based on SBR / NR rubber by injection molding. The technical parameters of the process are as follows:

Injection molding machine - Clamping force 850 IN

- Worm piston diameter 45 mm

- Screw rotation speed 90 rpm.

- Back pressure in 35%

- Cycle time 45 s

Injection mold - Fully automatic de-molding - Electric heating

178 383

Molding - open, directly injected through the riser system

- Multiplicity of 24

- Injection weight (with overhead) 0.064 kg

The plasticizing cylinder is equipped with three temperature control circuits which, according to the method according to the invention, are coupled to a control unit by means of thermal sensors placed in the cylinder wall. The circuit (fluid inlet) and circuit 3 (nozzle area) are equipped with additional heating. As time point Z, the start of the shaping hub was selected and as the time point Z2 the end of the mold opening motion was selected. The time between Z, Z2 is 37 s.

As the cylinder temperature set points for T _S ou introduced

For the perimeter (insertion zone): 45 ° C

For circuit 2 (heating and compacting zone, start of extrusion zone): 52 ^° C

For circuit 3 (extrusion zone and die tube): 60 ° C

The switch-on temperature for heating is T ^ 1 -2.5 K

The switch-off temperature is T ^ - - 2.0 K

The cylinder temperatures in the area of the respective temperature control circuits are measured approximately at the center of gravity of the cylinder wall, the so-called for a given inside diameter of 45 mm and for a given outside diameter of a cylinder of 90 mm approximately. 5 mm from the outside diameter in the radial direction and centered between the inlet and outlet of the temperature controlling medium for the circumference concerned. Temperature measurement is carried out continuously throughout the cycle. In the initial phase, after a few minutes, the temperature for switching off the additional heating is reached, and from that time up to the time points Z, individual cycles, pulses t ^ 0.3 s are introduced to cause the attenuated achievement of T _S o _U. When T _S oll is reached after the fifth cycle from the first violation to the top of the set temperature, the reference cycle is selected, thereby completing the initial phase.

The temperature control impulses calculated in the next cycles reach the duration of 2.0 - 5.5 s for the circuit, and 5.4 - 8.6 s for the circuits 2 and 3 under the influence of factors disturbing the thermal operating condition of the plasticizing cylinder.

All temperature control circuits are supplied with potable water from the plant's closed cooling water network, the inlet temperature being around f4 ° C. The use of a temperature regulating device is not necessary.

According to the method of the present invention, the previously mentioned moldings of the correct quality were produced in continuous operation with the following parameters:

Cycle time 45 s

Scrap rate 2.9%

Specific energy consumption 0.60 kWh / kg

Additional service costs for setting works per shift 22 min.

Comparative example k

The moldings as in Examples, and 4 were produced using a conventional temperature control method under the following temperature control conditions:

- Method of temperature control - 2 two-circuit additional temperature control devices

- Temperature regulating medium - in oda

- Medium temperature 2 x 55 ° C, 2x 60 ° C

The required cycle time was 37 s. With continuous operation, a scrap percentage of 34% was achieved, specific energy consumption of 0.72 kWh / kg.

Comparative example 2

The moldings as in Examples 2 and 5 were produced using a conventional temperature control method under the following temperature control conditions, the mold being thermally controlled by two additional temperature control devices:

178 383

Temperature control method -2 dual-circuit temperature control devices

- Temperature regulating medium - Water

- Medium temperature 2 x 50 ° C (nozzle side) x 45 ° C (movement side)

The required cycle time was 29 seconds. In continuous operation, the failure rate was 2.6%, and the specific energy consumption was 0.69 kWh / kg.

By using the method according to the invention, a markedly better process stability is achieved compared to the conventional temperature control method. In addition to the savings on the temperature regulating devices in both examples, the advantage is also in the reduction of the cycle time. According to these examples, the reduction was about 10%. As a result, a significant increase in production efficiency is achieved. The scrap percentage could also be significantly reduced. In these examples, the individual reductions in scrap percentage are 38 or 67%. Overall, a reduction of the specific energy consumption of 10-20% is thereby also achieved.

Comparative example 3

Fittings as in Examples 3 and 6 are produced using a conventional temperature control method with the following control conditions:

Temperature control method - one additional temperature control device, continuous temperature control on the entire plasticizing cylinder

- Temperature regulating medium - Water

- Medium temperature 75 ° C

The fittings mentioned in example 2 were produced in continuous operation with the following parameters:

Cycle time: 52 s

Scrap rate 4.2%

Specific energy consumption 0.70 kWh / kg

Additional maintenance work for adjustments per shift 37 min.

178 383

178 383

Fig. 2

178 383

L.

The degree of fit

ADU

Control of the firigitarry wfayfcgfri- Signals Z "Z, CPU

'1

Klańatira ifyśfcrietlacz

Fiig. 1

Publishing Department of the UP RP. Circulation of 70 copies

Price PLN 4.00.

Claims (17)

Patent claims A method of temperature control of injection molding units and mold sets for processing plastics, with at least one temperature control circuit, during which the temperature is measured at a specific location and as a result of comparing the set value with the actual value, the flow of the temperature control medium is changed, characterized in that temperature control is accomplished by a process including the following steps: - calculation of heat dissipation during the cycle by dividing the time between the time points Z _x and Z ₂ into equal parts, where the time points Zj and Z ₂ are previously determined by the machine control pulses, - preliminary determination of the desired heat dissipation, before starting temperature control, - continuous temperature measurement of the exhausted medium and the feeding medium, - determination of the heat value WRG contained in the device, when the device reaches thermal equilibrium, - saving the value of the contained heat in the next cycle as the desired value, based on the difference between the temperature of the medium exhausted and the temperature of the supply medium during the reference cycle, - comparing the desired value with the instantaneous actual value measured during all subsequent cycles, - determination of the correction value for the temperature control pulse triggered in a given cycle based on the heat content deviation from the reference cycle, in which the determined temperature control pulse starts at the time point Z _u, with the beginning thermostating process triggered at the time point Z _x , and the end pulse temperature control process triggered at the time point Z ₂ at the latest. 2. The method according to p. The process of claim 1, wherein the temperature of the mold is continuously measured at a location where the melt and the temperature regulating medium act equally. 3. The method according to p. The process of claim 1, wherein the temperature of the cylinder is continuously measured at a location where the heated molding material and the temperature-regulating medium act equally. 4. The method according to p. The method of claim 1, characterized in that when controlling the mold temperature of the injection molding machine, the start of the press-in time is set as the time point Z and the end of the mold opening movement as the time point Z2. 5. The method according to p. The method of claim 4, characterized in that the start of the injection operation is set as time point Z _x . 6. The method according to p. A method as claimed in claim 1, characterized in that when the temperature of the injection-molding cylinder is regulated, the plasticization start is set as time point Z _x and the end of the mold opening movement is set as time point Z2. 7. The method according to p. The method of claim 1, characterized in that the time points Z] and Z2 are determined by the same machine control pulse, the time point Z2 being the same as the time point Z _{x of the} next cycle. 8. The method according to p. The method of claim 1, characterized in that the temperature measuring point is located in the region of the geometric center between the contour of the compact and the temperature-regulating surface formed by the flow of the thermostating medium and in the region of the center between the inlet and outlet of the temperature-regulating medium at a distance from the contour of the compact. 9. The method according to p. The method of claim 1, characterized in that the temperature measuring point is situated in the region of the geometric center between the mold wall and the regulating surface The temperature formed by the flow of the thermostating medium and in the region of the center between the inlet and outlet of the temperature-regulating medium at a contour distance, the compact. 10. The method according to p. The method of claim 1, characterized in that the temperature measuring point is located in the area of the geometric center between the outer and inner wall of the cylinder, in the area central between the inlet and outlet of the temperature-regulating medium of the circuit concerned. 11. The method according to p. The process of claim 1, wherein the initial thermal equilibrium of the process is achieved by the following method steps: - in the first cycle of the process, to the time point Z, a pulse t _jn is introduced at a predetermined time to cause a first complete flush of the temperature control circuit - in the following cycles, the relative temperature control time t _d , depending on the desired thermal level, is divided into a certain number of initial pulses of different duration in the cycle, according to the following relationship td-anf = j * tm where: t _d - relative temperature control time j - number from 1 to mm - number of values from 5 to 10 for the thermal level, where 5 is the low thermal level and 10 is the high thermal level, with only one initial pulse per cycle , and the determined start pulses are introduced so often until the previously entered value t _d is reached, - when the value of td is reached, the integral WRG (Z ^ td) of the temperature course for that cycle is calculated and stored, - in the next cycle after the cycle in which the value of td was reached for the first time, the WRG integral is calculated, similarly to the previous stage (Zj, i.e. from the temperature course and compared with the stored, calculated value of this integral from the previous cycle, and if the difference is smaller than the value entered in _G , then this cycle is determined and stored as the reference cycle, and if the difference is equal to or greater than this value WRG (Z _b -tj, then the calculation of the integral with the value from the previous cycle is repeated in the following cycles, until the Wg value is exceeded and the start-up process is terminated. 12. The method according to p. A method according to claim 1, characterized in that it has additional steps during stationary operation in all cycles: - start of temperature control at time point Z _{1 of} each cycle with the relative duration of temperature control td, - temperature measurement of the supply stream and the exhaust stream continuously over successive and shorter time intervals, - calculation of the WRG integral (t, ₁ , t), - comparing the calculated integral with the reference cycle integral at an identical point in the cycle, - adjustments to the duration of the temperature control t _d in the current cycle based on a continuously determined difference. 13. The method according to p. The method of claim 1, characterized in that during the initial phase when entering a set point temperature which is lower than a certain actual temperature at all subsequent time points Z! and Z ₂ , the temperature is continuously controlled until the measured actual temperature for the first time drops below the entered set temperature, and after the set temperature is exceeded, the initial phase is continued by entering the temperature control pulse tan, at the time point Z, of the cycle following the first downward violation and ends when the set temperature is exceeded again and the reference cycle is selected later. 178 383 14. The method according to p. The process of claim 1, wherein additional heat is turned on, which turns off when the desired thermal level is reached. 15. The method according to p. 14. The process of claim 14, wherein the additional heating is activated before the start phase. 16. The method according to p. The process of claim 14, wherein the additional heating is turned on during the start-up phase. 17. The method according to p. A process as claimed in claim 14, characterized in that the additional heating is activated during the stationary phase of operation.